Tissue pressure measurement is now established as a valuable tool in the early detection of compartmental syndromes. Some controversy exists, however, with regard to the pressure at which surgical decompression becomes indicated. Furthermore, the pressure tolerance has been observed to vary among individuals. In order to better understand the factors determining pressure tolerance, we propose to investigate the effect of several conditions on the tolerance of neuromuscular tissue for increased pressure. These conditions include systemic hypoxia, hemorrhagic shock, major arterial occlusion, drug-induced hypotension, and steep pressure gradients between the compartment and the surrounding tissue. The investigation is to be carried out using a well-established animal model system in which known pressures are uniformly applied to rabbit hindlimbs. The physiological effects of this increased tissue pressure are to be characterized by continuously monitoring the muscle pO2, muscle pCO2, and muscle blood flow as well as the myoneural conduction velocity. It is anticipated that these investigations will improve the understanding of the pathophysiology of compartmental syndromes and improve the clinical usefulness of tissue pressure measurements in the evaluation of patients at risk for these conditions.